Added
* `py.typed` file for PEP-561 compatibility
* docs: Supported standards
* Loader.__iter__() method.
Changed
* docs: license.md renamed to LICENSE.md
Infrastructure
* Adopt ruff
* Use `actions/checkoutv3`
* Use `actions/cachev3`
* Project structure tests
* CI workflows tests
* Extend licence copyright years
* Dockerfile: Use `set -x` to log RUN commands
* docs: Use common Gufo Labs mkdocs plugins set